This application claims benefit of Japanese Patent Application No. 2000-185500 filed on Jun. 20, 2000, the contents of which are incorporated by the reference.
The present invention relates to digital circuit multiplexing equipment (hereinafter referred to as DCME) and, more particularly, to facsimile signal transmission systems for the same, which are capable of updating the control of a signal identification (discrimination) circuit and also the demodulation control of a facsimile (hereinafter referred to as FAX) signal allotment (assignment) control circuit with respect to non-prescribed FAX protocols.
Among systems of FAX signal transmission via the DCME is a method of executing a DCME FAX signal compression and transmission process, which is prescribed in “FCH protocol”, Section 6.2.2. in “Facsimile Demodulation/Redemodulation for Digital Multiplication Equipment”, ITU-T Recommendation G.766.
The ITU-T Recommendation G.766 itself adopts as its basic protocol “Procedure for Document Facsimile Transmission in the General Switched Telephone Network”, ITU-T Recommendation T.30, which prescribes inter-FAX protocol control.
FIG. 11 shows the construction of a prior art transmission side of DCME for executing the above basic protocol. As shown, this DCME transmission side has a general construction comprising a signal identification circuit 51, a delay circuit 52, a voice/data allotment control circuit 53, a voice/data ADPCM (Adaptive Differential Pulse Code Modulation) coding circuit 54, a voice/data transmission circuit 55, a voice/data allotment signal generation circuit 56, a delay circuit 57, a FAX data allotment control circuit 58, a FAX data demodulation circuit 59, a FAX data transmission circuit 60, a FAX allotment signal generation circuit 61 and a multiplexing circuit 62.
In the transmission side shown in FIG. 11, a trunk (“TRUNK”) signal from a switching station side (not shown), is inputted via a trunk signal input terminal to the signal identification (discrimination) circuit 51. The signal identification circuit 51 outputs a voice/data identification signal when it identifies (discriminates) the input signal to be a voice signal or a data signal, and outputs a FAX data identification signal when it identifies the input signal to be a FAX data signal. According to the voice/data identification signal from the signal identification circuit 51, the voice/data allotment (assignment) control circuit 53 outputs a delay control signal to the to the delay circuit 52, outputs a voice/data ADPCM coding control command to the voice/data ADPCM coding circuit 54, outputs voice/data signal transmission command to the voice/data signal transmission circuit 55, and outputs a voice/data allotment command to the voice/data allotment signal generation circuit 56. In this way, the circuit 53 effects allotment control of the above pertinent circuits. The delay circuit 52 delays the input signal by a time necessary for the identification of the input signal, and outputs the resultant delayed voice/data signal to the voice/data ADPCM coding circuit 54. In the circuit 54, the pertinent ADPCM coding circuit selected according to the ADPCM coding control command from the voice/data allotment control circuit 53, executes an ADPCM coding process on the allotted (assigned) voice or data signal, and outputs the resultant voice/data ADPCM signal to the voice/data transmission circuit 55. The circuit 55 rearranges the input voice/data signal obtained by the ADPCM coding process, and transmits the resultant signal as voice/data transmission signal to the multiplexing circuit 62 for the multiplexing. The voice/data allotment signal generation circuit 56 generates a voice/data allotment signal, and transmits this signal to the multiplexing circuit 62 for the notification of voice/data allotment data to the opposite side of communication.
Likewise, according to the FAX data identification signal inputted from the signal identification circuit 51, the FAX data allotment control circuit 58 outputs a delay control signal to the delay circuit 57, outputs a FAX data demodulation control command to the FAX data demodulation circuit 59, outputs a FAX data transmission command to the FAX data transmission circuit 60, and outputs a FAX data allotment command to the FAX data allotment signal generation circuit 61. In this way, the circuit 58 effects allotment control of the above pertinent circuits. The delay circuit 57 delays the input signal by a time necessary for the identification, and outputs the resultant delayed FAX data signal to the FAX data modulation circuit 59. In the circuit 59, the pertinent FAX data demodulation circuit selected according to the FAX data demodulation control command, executes a FAX data demodulation process, and outputs the resultant FAX data demodulation signal to the FAX data transmission circuit 60. The FAX data transmission circuit 60 rearranges the input FAX data demodulation signal, and transmits this signal to the multiplexing circuit 62 for multiplexing. The FAX allotment signal generation circuit 61 generates and outputs a FAX allotment signal for the notification of FAX data allotment data to the opposite side of communication. The multiplexing circuit 62 multiplexes the voice/data transmission signal, the voice/data allotment signal, the FAX data transmission signal and the FAX data allotment signal, and transmits a resultant bearer as compression coded output signal to the opposite side of communication.
FIG. 12 shows the construction of a prior art reception side of DCME for executing the above basic protocol. As shown, this reception side has a general construction comprising a separating circuit 63, a voice/data signal output circuit 64, a voice/data allotment signal reception circuit 65, a voice/data distribution control circuit 66, a voice/data ADPCM demodulation circuit 67, a FAX data signal output circuit 68, a FAX allotment signal receiving circuit 69, a FAX distribution control circuit 70, a FAX signal remodulation circuit 71 and a signal output circuit 72.
In the reception side shown in FIG. 12, the multiplexed input bearer signal is inputted to the separating circuit 63. The separating circuit 63 separates voice/data transmission signal, voice/data allotment signal, FAX transmission signal and FAX allotment signal from the input bearer signal. The voice/data allotment signal reception circuit 65 performs analysis of the voice/data allotment signal to output a voice/data allotment analysis signal. The voice/data distribution control circuit 66 outputs a voice/data signal control command and a voice/data ADPCM decoding control signal according to the allotment analysis signal for distribution control of the voice/data signal output circuit 64 and the voice/data ADPCM decoding circuit 67, respectively. The voice data output circuit 64 rearranges the voice/data transmission signal according to the voice/data signal output control command, and outputs a resultant rearranged voice/data ADPCM decoded signal for an ADPCM decoding process. The voice/data ADPCM decoding circuit 67 performs an ADPCM decoding process on the pertinent signal in the voice/data ADPCM decoding signal according to the voice/data ADPCM decoding control signal, and outputs the resultant decoded voice or data signal to the signal output circuit 72.
The FAX allotment signal reception circuit 69 performs analysis of the FAX allotment signal separated in the separating circuit 63, and outputs a FAX allotment analysis signal. The FAX distribution control circuit 70 outputs a FAX data signal output control command and a FAX data signal remodulation control command according to the FAX allotment analysis signal for distribution control of the FAX data signal output circuit 68 and the FAX data signal remodulation circuit 71. The FAX data signal output circuit 68 rearranges the FAX data demodulation signal according to the FAX data signal output command, and outputs a resultant FAX demodulation signal for a FAX data signal remodulation process. The FAX data signal remodulation circuit 71 performs a remodulation process of the pertinent signal in the FAX demodulation signal according to the FAX data signal remodulation control command, thus generating a FAX remodulation signal.
The signal output circuit 72 outputs the demodulated voice signal, the decoded data signal and the remodulated FAX remodulation signal to respective trunks to be outputted via a trunk signal output terminal to a switching station (not shown).
The prior art DCME, however, has a problem that on the transmission side the FAX data signal discrimination control cannot be freely set.
This problem arises from the fact that the transmission side of the DCME does not have a function of freely setting a FAX data signal identification function. Therefore, the signal identification function of the FAX module for processing the FAX data signal, is such that processing is possible only with a fixed FAX protocol prescribed in ITU-T G.766. Therefore, when a non-prescribed FAX protocol is inputted or when ITU-T G.766 is updated, erroneous identification of a FAX data signal capable of being processed or demodulation control disability may arise, and in the extreme case it becomes necessary to execute an inter-FAX terminal cut-off process.